This invention relates to prevention of foaming in lubrication oil.
Lubrication oil in automotive differentials and gear boxes of industrial machines frequently foams after prolonged use. When the lubrication oil foams, its volume greatly increases and thus part of the oil is forced out of the gear housing through breather holes and the like. Beside causing a loss of oil, foaming also interrupts the proper lubricating function of the oil and so results in rapid wear in the various components of the gear train.
It has been found that foaming occurs when water has been present for sometime in the lubrication oil in a gear box. Water itself does not cause this foaming as no foaming is observed when lubrication oil is agitated in the presence of water deliberately added to the oil. Experiments indicate that water in lubrication oil reacts with the steel surface of the gear trains and of other components in a gear box to form ferric-hydroxide. The rate at which such a reaction takes place depends on temperature, and it may take a considerable period of time before ferric hydroxide is found in any appreciable amount. The ferric hydroxide formed, being basic, will react with various acidic additives commonly present in lubrication oils. Among such additives, sulphur type and, in particular, phosphorous type additives have been found to react with ferric hydroxide to form a reaction product, in the presence of which the lubrication oil will foam after a certain amount of agitation. The exact nature of this reaction product is not known, and such reaction product will be generally referred to hereinafter as metallic salts. The amount of water normally present in lubrication oils may vary considerably. Experiments leading to this invention showed that 0.05% of water is sufficient to lead to subsequent foaming.
The object of this invention is to prevent foaming in lubrication oils.